In laparoscopic surgery, suturing and ligating requires the introduction of suture material into the abdominal cavity by passing the suture through a trocar. After introduction of the suture into the body cavity, the distal end of the suture material is then grasped with a grasper instrument to form either an endosuture (with a needle) or endoligature (without a needle). The grasper tool in one technique may be used to grasp the needle, snare the body structure, and then form a slip-knot intracorporeally; in another technique the free end of the suture material may be looped around a body structure such as a tube or vessel thereby forming a bight and the free end withdrawn through the trocar for the formation of an extracorporeal slip-knot. A push rod is then used in either technique to tighten the slip-knot by pushing the knot toward the body structure.
In the prior art, where the slip-knot is formed using a needle, one type of push rod utilized an axially extending lumen through which the strand of suture material above the slip-knot was inserted extracorporeally; the push rod was then pushed to tighten the knot. Where the slip-knot was formed extracorporeally without the needle, however, push rods generally utilized a longitudinally extending slot contained in the outer surface and located at the distal end of the rod; this permitted the strand of suture above the slip-knot to be advanced through the slot while the tip of the push rod remained in continuous engagement with the slip-knot as the knot was advanced into the body cavity through the trocar. In pushing a slip-knot formed extracorporeally through the trocar, however, the strand of suture contained in the slot above the slip-knot, during manipulation of the push rod, has a tendency, depending upon the orientation of the push rod, to slip from the groove; this requires the upper strand of suture material to be rethreaded by the surgeon into the slot in order to continue to advance and thereafter tighten the knot. If the strand slipped from the slot while the knot was in the trocar, it was usually necessary to withdraw the rod, reinsert the suture strand into the slot and then advance the rod through the trocar until engagement with the knot. This procedure was time consuming and unreliable and resulted in the escape of CO.sub.2 gas from the body cavity. Thus, the method of the prior art for pushing a knot formed extracorporeally through a trocar into the operative cavity increased the operative risk because of the additional time required to thread the strand of the suture material into the slot and then re-engage contact with the slip-knot for advancement through the trocar.